After running well on his three-year-old debut he produced a series of disappointing efforts before recording an upset victory over a strong field in the St Leger.
Julio Mariner was an exceptionally good-looking bay[1] horse with no white markings[2] bred in Wiltshire by the Fonthill Stud which was managed by James Ian Morrison.
[6] Julio Mariner made his debut in the Acomb Stakes at York Racecourse in August when he lost a great deal of ground at the start and finished unplaced.
In the Sancton Stakes over seven furlongs at the same venue later that month he was beaten a short head by Tannenberg, with the two finishing twelve lengths clear of the other runners.
In a rough race, Julio Mariner was repeatedly blocked before being switched to the wide outside by his rider Eddie Hide to obtain a clear run in the last quarter mile.
[7] In the King Edward VII Stakes at Royal Ascot he finished unplaced behind Classic Example and then won a minor race over one mile at York.
In the Benson and Hedges Gold Cup at York in August he was equipped with blinkers but made little impact, finishing eighth of the ten runners behind Hawaiian Sound.
In a change of tactics, Hide retrained the colt at the back of the fourteen runner field before beginning to move forward approaching the final turn.